v1.4.0 (2026-07-15)

Security

• Upgraded com.fasterxml.jackson.core dependencies to version 2.21.5 to address multiple CVE's in previous releases.

New Features

• Internal buffering now supports exactlyOnce=true via strict-chunking mode. When both bufferCount > 0 and
  exactlyOnce=true, records are bucketed per (topic, partition) and flushed only in fixed bufferCount-sized
  chunks. Tail records below the threshold remain buffered until subsequent put() calls grow the bucket past
  bufferCount. This keeps (minOffset, maxOffset) reproducible across retries, allowing ClickHouse
  insert_deduplication_token reuse and StateProvider range comparison to work correctly. Requires bufferFlushTime=0
  and ignorePartitionsWhenBatching=false — the start-up validator throws ConnectException otherwise.

Improvements

• Cast/conversion failures in ClickHouseWriter now surface the failing column and its types.
  Previously a type mismatch (e.g. a java.util.Date reaching a UInt64 column) threw a bare
  ClassCastException that named only Java types, and the useful context — column name, target
  ClickHouse type, source Kafka type — was written to the container logs only. The connector now
  rethrows these as a non-retryable DataException carrying that context, so it also reaches the Kafka
  Connect REST status, DLQ record headers, and JMX task-error-metrics. Record values are never
  included in the message. (#729)

Internal Changes

• Refactored ClickHouseSinkTask to delegate to a DeliveryStrategy per delivery semantic (DirectDeliveryStrategy,
  AtLeastOnceBufferStrategy, ExactlyOnceBufferStrategy), with a shared ChunkFlusher for the insert +
  offset-tracking path. The buffering and non-buffering flows now live in separate, cohesive units instead of
  interleaved branches on the task. Behavior is unchanged.

Bug Fixes

• Fixed NullPointerException when writing a null value into a Nullable(JSON) column via the binary
  insert path with input_format_binary_read_json_as_string=1. The JSON case in ClickHouseWriter cast the
  field straight to String without checking for null first, unlike every other nullable-aware type in the
  same switch. (#562)

Dependencies

• Bumped org.json:json from 20250517 to 20260522.